1. Technical Field
The present invention relates to a multi-gap rotating electric machine capable of effectively cooling a stator coil.
2. Description of Related Art
There are known rotating electric machines which are used in a narrow space and thus required to be flat in shape, such as an engine direct-coupled motor that is arranged between an engine and a transmission in a motor vehicle. Moreover, for increasing the output torque, these rotating electric machines are configured as multi-gap rotating electric machines which have a plurality of magnetic gaps formed therein.
For example, Japanese Patent Application Publication No. JP2014176203A discloses a double-stator motor which is configured to include a rotor and inner and outer stators. The inner stator is disposed radially inside the rotor with a radially inner magnetic gap formed between the inner stator and the rotor. The outer stator is disposed radially outside the rotor with a radially outer magnetic gap formed between the outer stator and the rotor. With this configuration, it is possible for the double-stator motor to generate higher torque than a single-stator motor.
Moreover, the double-stator motor has a cooling structure provided therein. Specifically, the double-stator motor has: a first cooling oil introduction passage formed in a rotating shaft of the motor to introduce cooling oil from the outside of a housing of the motor to a radially inner cooling space formed between a radially inner surface of an inner stator core and a radially outer surface of a large-diameter portion of the rotating shaft; a second cooling oil introduction passage formed in a ceiling part of the housing to introduce cooling oil from the outside of the housing to a radially outer cooling space formed between a radially outer surface of an outer stator core and an interior circumferential surface of the housing; and a third cooling oil introduction passage formed in the ceiling part of the housing to introduce cooling oil from the outside of the housing to a side cooling space formed between a side surface of a side stator core and an interior side surface of the housing. In operation, cooling oil is introduced from the outside of the housing to the radially inner, radially outer and side cooling spaces via the first to the third cooling oil introduction passages, thereby cooling the inner, outer and side stator cores.
Furthermore, in the third embodiment of the above patent document, a plurality of arc-shaped protrusions are formed on an upper part of the interior side surface of the housing to guide the cooling oil introduced to the side cooling space to circumferentially spread.
With the arc-shaped protrusions, it is possible to reliably supply the cooling oil to an upper part of a side stator coil which is located above the central axis of the rotating shaft, thereby effectively cooling the upper part. However, since there are no cooling oil guide members provided below the central axis of the rotating shaft, it may be difficult to reliably supply the cooling coil to a lower part of the side stator coil which is located below the central axis of the rotating shaft. Consequently, it may be difficult to effectively cool the lower part of the side stator coil.